The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
The present disclosure relates generally to wellbore treatment and development of a reservoir and, in particular, to a system and a method for determining characteristics of the reservoir during a wellbore operation such as, but not limited to, a wellbore treatment operation, an underbalanced drilling operation, or the like.
Currently, fiber optic Distributed Temperature Sensing (DTS) technology provides a means for substantially instantaneous temperature measurement in a wellbore. DTS typically includes an optical fiber disposed in the wellbore (e.g. via a permanent fiber optic line cemented in the casing, a fiber optic line deployed using a coiled tubing, or a slickline unit). The optical fiber measures a temperature distribution along a length thereof based on an optical time-domain (e.g. optical time-domain reflectometry (OTDR), which is used extensively in the telecommunication industry).
One advantage of DTS technology is the ability to acquire in a short time interval the temperature distribution along the well without having to move the sensor as in traditional well logging which can be time consuming. DTS technology effectively provides a “snap shot” of the temperature profile in the well. DTS technology has been utilized to measure temperature changes in a wellbore after a stimulation injection, from which a flow distribution of an injected fluid can be qualitatively estimated.
The introduction of hot slugs in a wellbore is another useful technique for flow profiling with Distributed Temperature Sensing (DTS). The conventional method of generating a hot slug includes injecting a large fluid volume in the reservoir and then shutting the well in to heat the fluids above the reservoir interval. The temperature of the fluids next to the reservoir interval increase much slower as the reservoir interval is much cooler because of fluids injected previously. This differential heating creates a temperature front that can be tracked with DTS for flow profiling.
By obtaining and analyzing multiple DTS temperature traces, the characteristics and flow properties of different formation layers can be determined.
Several methods for quantitatively characterizing a reservoir and determining the flow distribution therein from a DTS measurement are discussed in detail below.